Magnetic ordering in the frustrated J1-J2 Ising chain candidate BaNd2O4

TL;DR

This study investigates the magnetic ordering in BaNd₂O₄, revealing long-range collinear spin order in one Nd chain type and field-induced transitions, consistent with classical Ising chain models.

Contribution

It provides the first detailed neutron diffraction analysis of BaNd₂O₄, identifying specific magnetic structures and field-induced phases in this frustrated magnetic system.

Findings

Long-range magnetic order observed below 1.7 K.

Two field-induced spin transitions at 2.5 T and 4 T.

Magnetic structure consistent with classical Ising chain model.

Abstract

The AR$_2$O$_4$ family (R = rare earth) have recently been attracting interest as a new series of frustrated magnets, with the magnetic R atoms forming zigzag chains running along the $c$-axis. We have investigated polycrystalline BaNd$_2$O$_4$ with a combination of magnetization, heat capacity, and neutron powder diffraction (NPD) measurements. Magnetic Bragg peaks are observed below $T_N$ $=$ 1.7 K, and they can be indexed with a propagation vector of $\vec{k}$ $=$ (0 1/2 1/2). The signal from magnetic diffraction is well described by long-range ordering from only one of the two types of Nd zigzag chains, with collinear up-up-down-down intrachain spin configurations. Furthermore, low temperature magnetization and heat capacity measurements reveal two field-induced spin transitions at 2.5 T and 4 T for $T$ $=$ 0.46 K. The high field phase is paramagnetic, while the intermediate field state may arise from a spin transition of the long-range ordered Nd chains, resulting in an up-up-down intrachain spin configuration. The proposed intermediate field state is consistent with the magnetic structure determined in zero field for these chains by NPD, as both phases are predicted for the classical Ising chain model with nearest neighbor and next nearest neighbor interactions.